Dual fuel supply systems for supplying a fuel mixture of diesel and gaseous fuel to diesel engines are known. Some dual fuel supply systems introduce the gaseous fuel into the air supply that leads to the combustion chamber. In US2005202021 a separate set of injectors introduce gaseous LPG into the combustion chamber, whereas in U.S. Pat. No. 5,408,957, U.S. Pat. No. 4,520,766, JP1318755 and GB1252458, gaseous LPG is mixed with air prior to introducing the air mixture to the combustion chamber.
The use of LPG and diesel at the same time has recently been addressed by the dual fuel system disclosed in WO 2008036999 where liquid LPG and diesel were mixed in a chamber prior to being introduced into the combustion chambers. However there are problems associated with the dual fuel system disclosed in WO 2008036999 in its application with different engine types.